Solid state membrane channel device for the measurement and characterization of atomic and molecular sized samples

ABSTRACT

A solid state device is formed through thin film deposition techniques which results in a self-supporting thin film layer that can have a precisely defined channel bored therethrough. The device is useful in the chacterization of polymer molecules by measuring changes in various electrical characteristics as molecules pass through the channel. To form the device, a thin film layer having various patterns of electrically conductive leads are formed on a silicon substrate. Using standard lithography techniques, a relatively large or micro-scale aperture is bored through the silicon substrate which in turn exposes a portion of the thin film layer. This process does not affect the thin film. Subsequently, a high precision material removal process is used (such as a focused ion beam) to bore a precise nano-scale aperture through the thin film layer that coincides with the removed section of the silicon substrate.

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] The present application is a continuation in part of ProvisionalApplication Serial No. 60/191,663, filed Mar. 23, 2000, which is hereinincorporated by reference in its entirety.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The present invention relates to a device for thecharacterization of polymer molecules. More specifically, the presentinvention relates to a solid state device useful for thecharacterization of polymer molecules as well as a method of making thesame.

[0004] 2. Description of the Related Art

[0005] It has recently been announced that the mapping of the humangenome has been completed. This historic development will lead to amyriad of developments ranging from the identification of the geneticbasis of various diseases to the formulation and fabrication of newdrugs and treatment protocols. All of this will only further serve toincrease the already high demand for rapid information processingrelating to polymer characterization, particularly that of variousnucleic acids (i.e., DNA).

[0006] Heretofore, the sequencing of nucleic acids has been performedthrough chemical or enzymatic reactions. This allows for the nucleicacids to be separated into strains having differing lengths. This isgenerally tedious and laborious work and requires a significant amountof time and effort to complete. Thus, the results from any desiredcharacterization of a particular polymer sequence are usually quiteexpensive and take a fair amount of time to obtain.

[0007] A significant advancement in the characterization of polymermolecules was introduced by Church et al. in U.S. Pat. No. 5,795,782which issued on Aug. 18, 1998. Church et al. teach a method of causingpolymer molecules, and in particular nucleic acids, to pass through anion channel in an otherwise impermeable organic membrane. The membraneseparates two pools of a conductive fluid solution containing a supplyof the polymer material in question. By generating a voltagedifferential across the membrane, the polymer molecules can be ionizedor polarized and guided through the ion channel. By measuring thevarious electrical characteristics of the membrane, the particular baseof the polymer molecule can be identified by identifying the changes inthese electrical characteristics as a particular base of the polymermolecule occludes the channel. Thus, each type of base member willexhibit unique characteristics that are identifiable by variations inmonitored electrical parameters such as voltage or current.

[0008] The drawback of this device is that it is difficult to create animpermeable membrane having a sufficiently small ion channel that willallow the device to function properly. Church, et al. teaches using anorganic membrane where an ion channel is created through the membranevia a chemical etching process. This is extremely difficult to do on acost effective and repetitive scale. Specifically, the formation of anotherwise impermeable organic membrane and chemically etching orotherwise forming the ion channel is a hit or miss operation that may ormay not actually produce the appropriately channeled membrane. Thus,while the concept of providing for the rapid determination of thecharacter of polymer molecules is an extremely important one, no devicehas been provided that can be reliably produced while achieving accurateresults.

[0009] Therefore, there exists a need to provide a high quality,reliable and easily reproducible polymer characterization device.

SUMMARY OF THE INVENTION

[0010] The present invention provides a generally impermeable membranehaving a nano-scale aperture. Polymer molecules are caused to travelthrough the aperture or channel and the electrical characteristicsgenerated by the particular base or monomer occupying the channel at agiven time is determined based upon various measurements made bymonitoring the membrane.

[0011] In one embodiment, the membrane is used to separate two pools ofa conductive medium containing quantities of the polymer molecules inquestion. Unlike membranes used by the previous device which are organicin nature, the membrane of the present invention is inorganic and uses acombination of wafer and thin film technology to accurately andconsistently manufacture a membrane having the desired characteristics.The membrane is formed by providing a base preferably using a siliconsubstrate. A thin film is deposited on one side of the siliconsubstrate. The thin film includes one or more integrated electricalleads that can ultimately be connected to the testing and monitoringequipment. Using standard lithography techniques and taking advantage ofthe anisotropic etching characteristics of single crystal siliconwafing, a micro-scale hole is etched through the silicon substrate. Inthe selected area, the etching process removes all of the siliconsubstrate but leaves the thin film entirely intact and unaffected. Thus,a self supporting thin film, such as SiN for example is bridged across amicro-scale aperture in a silicon substrate. Using a focused ion beam orelectron beam lithography, a nano-scale aperture is precisely cutthrough the thin film layer. Thus, the nano-scale aperture provides achannel through which polymer molecules pass and are measured in variousways.

[0012] The present invention also provides for differing configurationsof the thin film layer. At a minimum, a single electrically conductivelayer should be provided. If properly configured, the fabrication of thenano-scale aperture will bisect this conductive layer into twoindependent and electrically isolated conductive members or leads. Thus,as a molecule passes through the channel, monitoring equipment connectedto each of the electrically conductive sections can obtain measurementssuch as voltage, current, capacitance or the like. This would be atransverse measurement across the channel.

[0013] In practice, it may be more practical to provide one or moredielectric layers that effectively protect and insulate the conductivelayers. The use of such dielectric layers can simplify the manufacturingprocess and allows for multi-level conductive layering to be generated.That is, providing a single conductive layer or effectively providingelectrical leads in a common plane allows for measurements of theparticular polymer base in a transverse direction. However, by stackingconductive layers atop on another (electrically isolated from oneanother such as by an interposed dielectric layer), measurements ofcertain electrical characteristics can be taken in the longitudinaldirection.

[0014] The present invention provides for a variety of lead patterns inboth a longitudinal and transverse direction. In one embodiment, asingle, shaped electrically conductive layer is provided. The conductivelayer is relatively narrow near a medial portion so that a channelformed therethrough by a focused ion beam effectively bisects theelectrically conductive layer into two electrically independent sectionsor leads. The benefit of such a construction is a minimal number ofsteps are required to complete the finished product. However, onepotential drawback is that the single conductive layer must be appliedrelatively precisely in that the channel which eventually separates thelayer in two will usually have a diameter on the order of tennanometers.

[0015] Since this level of precision may be difficult in somemanufacturing processes, another single layer approach is provided.Namely, a single electrically conductive layer is provided. However, themedial portion need not be so narrow as to allow bisection by theformation of a nano-scale aperture. Thus, when a nano-scale aperture isbored through the thin film layer, electrically conductive materialremains which effectively connects the two leads. A focused ion beam orother precision material removing apparatus is used to remove a sectionof the thin film layer so that the two leads are electricallyindependent.

[0016] By providing leads on a single plane, various transversemeasurements of electrical characteristics can be performed. Bisecting asingle layer results in the formation of two leads. The presentinvention also provides for fabricating four or more leads in a singleplane so that multiple transverse measurements are possible.

[0017] By utilizing dielectric layers, electrically conductive leads canbe fabricated in multiple planes. This not only allows for transversemeasurements to be made, but facilitates longitudinal measurements aswell. Any configuration or variation of the single plane lead structurescan be repeated with the multi-level thin film layers. Namely,relatively precise conductive layers can be applied relying on thefocused ion beam or other precision cutting device to bisect eachrespective layer. Alternatively, a focused ion beam or other precisioncutting device can be utilized for removing a precise amount of theelectrically conductive layer in and around the desired channel area,once again resulting in any number of leads being fabricated in anygiven plane. Thus, multiple transverse and multiple longitudinalmeasurements can be made between any given pair of leads.

[0018] Longitudinal measurements in and of themselves may be sufficientto determine the necessary characteristics in the polymer material inquestion. That is, it is not necessary to have electrically isolatedlead pairs in a single plane. This allows for an embodiment where arelatively imprecise electrically conductive layer is formed in a firstplane. A second relatively imprecise electrically conductive layer isformed in a second plane wherein the second plane is separated from thefirst by a dielectric layer. By providing a nano-scale aperture throughthe entirety of the thin film layer (i.e., the dielectric layers andboth the conductive layers), a completed structure is fabricated. Inthis embodiment, electrical measurements are not possible within asingle plane. However, by measuring across different planar levelssufficient information may be gathered to characterize the polymermolecule. This configuration provides for relative ease during themanufacturing process and results in a repeatable and highly accuratedevice.

BRIEF DESCRIPTION OF THE DRAWINGS

[0019]FIG. 1 is a schematic illustration of a membrane separating mediumbearing pools containing linear molecules wherein the linear moleculespass through a channel in the membrane and are detected by the attachedelectronic testing equipment.

[0020]FIG. 2A is an end view of a silicon substrate.

[0021]FIG. 2B is an end view of a silicon substrate with a thin filmlayer applied thereto.

[0022]FIG. 2C is a partially sectional end view of a silicon substratehaving a lithography hole bored therethrough with a self supporting thinfilm layer atop the silicon substrate.

[0023]FIG. 2D is a schematic view illustrating the orientation of afocused ion beam used to cut a channel through the thin film layer.

[0024]FIG. 2E is a silicon substrate bearing a self supporting thin filmlayer having a nano-scale channel bored therethrough.

[0025]FIG. 3 is a sectional view of a thin film layer having aconductive layer disposed between two dielectric layers.

[0026]FIG. 4 is a top view of a conductive layer having two leads with anano-scale channel bored therethrough.

[0027]FIG. 4A is a top view of a conductive layer having two leads witha nano-scale channel bored therethrough.

[0028]FIG. 4B is a side elevational view of a silicon substrate with apartially self supporting layer sandwiched between two conductivelayers.

[0029]FIG. 5 is a top view of an electrically conductive layer havingtwo leads and a nano-scale aperture bored therethrough wherein dashedlines are used to indicate excess material that must be removed toelectrically isolate the two leads from one another.

[0030]FIG. 6 is a top view of a shaped, electrically conductive layer.

[0031]FIG. 7 is a top view of an electrically conductive layer separatedinto orthogonal lead pairs with a nano-scale aperture boredtherethrough.

[0032]FIG. 8 is a sectional view of a thin film layer having dualelectrically conductive layers.

[0033]FIG. 9 is a top view of the conductive layers forming the dualconductive layer thin film of FIG. 8.

[0034]FIG. 10 is a top view of two electrically conductive layers oneatop another with a nanoscale channel board therethrough.

[0035]FIG. 11 is a schematic illustration of a dual conductive layerthin film and a silicon substrate forming a membrane separating an upperand lower medium bearing liquid.

[0036]FIG. 12 is a schematic illustration illustrating a thin filmhaving dual conductive layers coupled with a silicon substrateseparating an upper and lower medium bearing pool.

DETAILED DESCRIPTION OF THE INVENTION

[0037] Referring to FIG. 1, a channel device is illustrated andgenerally referred to as 10. Channel device 10 includes container 15within which resides a volume of fluid. The fluid is separated into anupper pool 20 and lower pool 25 by a membrane 30. The liquid withinupper pool 20 and lower pool 25 is preferably a conductive solution andcontains a number of linear polymer molecules 40. Polymer molecules 40are free to travel through the liquid medium contained within container15. FIG. 1 is provided for illustrative purposes only and the componentsshown are not drawn to scale in general or with respect to each other.

[0038] By using various processes, such as introducing a voltagedifferential across membrane 30, polymer molecules 40 can be directedthrough channel 35 in membrane 30. Channel 35 is a nano-scale aperture.Typically, channel 35 will have a diameter of up to about 10 nm andpreferably between 2-4 nm. Of course, the actual size will be selectedto best serve the desired application. As linear polymer molecule 40travels through channel 35, the individual monomers will interact withmembrane 30 within channel 35. This will result in various electricaland/or physical changes that can be detected by the electronic testingequipment 50 that is interconnected with membrane 30 through leads 45.For example, a given monomer within channel 35 can be determined bychanges in measured voltage, conductance, capacitance or various otherelectrical parameters. Thus, as polymer molecule 40 passes throughchannel 35, each individual monomer is characterized. As this data isreceived and stored, the character of the polymer is accuratelyidentified. In previously known devices utilizing this technique, themembrane consists of a difficult to manufacture and delicate organicmembrane hopefully having an appropriately sized channel chemicallyetched therethrough. Fabricating an otherwise impermeable organicmembrane is a difficult and inconsistent process. It is even moredifficult to chemically create a single or a controlled number ofchannels therethrough while of course maintaining the proper dimensionsin the fabricated channel. Finally, connecting testing equipment andmaking electrical measurements from such a membrane is exceedinglydifficult. Thus, the present invention provides a reliable, mechanicallyfabricated inorganic membrane 30.

[0039]FIG. 2A illustrates the first step in the process of fabricatingmembrane 30. A supportive substrate 55 is provided. Preferably,substrate 55 is a self supporting member constructed of an etchablematerial. An ideal material is silicon and, in particular, siliconwafers which are widely available and easy to work with. It should benoted that all of the Figures only illustrate components schematically.Thus, the scale imparted bears no relationship to actual practice.Furthermore, the scale of the components as compared to one another isskewed so as to illustrate concepts.

[0040] In FIG. 2B, a thin film 60 is deposited on one surface of siliconsubstrate 55. Thin film 60 is shown as a single layer, however itsactual construction can be more complicated and will be explained ingreater detail below. After thin film 60 has been generated on siliconsubstrate 55, a hole 65 is etched into the silicon substrate 55 usingstandard lithography techniques, such as wet etching. Such techniqueswill remove the silicon in the desired area but will have no effect onthin film 60. Thus, over the area defined by lithography hole 65, thinfilm layer 60 becomes self supporting as illustrated in FIG. 2C.Subsequently, a channel 75 (as illustrated in FIG. 2E) is cut throughthin film 60 with a focused ion beam (FIB) 70 or other suitableprecision milling device such as electron beam lithography, neutralparticle beam, charged particle beam, x-ray, or other suitablemechanism.

[0041] When using a FIB, the aspect ratio between the thickness of thethin film and the size of the channel 75 must be considered. That is, aFIB can only mill so deep while maintaining a particular diameterchannel. Typical FIB devices have an optimal range of about 1:2, and arefunctional to about 1:4. Thus, the thickness of this film 60 should beselected to be in accordance with the limitations of the FIB (or thealternative milling device) actually being utilized. Thus, for a channel75 having an approximate diameter of 10 nm, an optimal thin film 60thickness would be less than 20 nm (1:2) to less than 40 nm (1:4). Theresult as illustrated in FIG. 2E is a completed membrane 30 having abase or silicon substrate 55 with a relatively large (micro-scale)lithography hole 65 on top of which resides a partially self supportingthin film layer 60 having a nano-scale aperture or channel 75 boredtherethrough. As illustrated, channel 75 and lithography hole 65 arealigned so that passage through channel 75 is in no way impeded by anyportion of the remaining silicon substrate 55. As explained in greaterdetail below, thin film layer 60 has electrically conductive portionswhich may be coupled to testing equipment. This may be accomplished byproviding a conductive thin film layer on one or both sides of selfsupporting membrane 60. Thus, various electrical characteristics of thinfilm 60 can be monitored by the testing equipment. When membrane 30 asillustrated in FIG. 2E is actually used in a polymer moleculecharacterization device 10, thin film layer 60 effectively acts as themembrane, as silicon substrate 55 is essentially a support member.Depending upon the fluid medium selected, it may be desirable to provideadditional material around silicon substrate 55 to protect it. Forexample, Teflon® or other suitable materials could be utilized.

[0042] Referring to FIG. 3, thin film 60 is shown in more detail. FIG. 3is a sectional view of a multi-layer thin film having electricallyconductive layer 85 disposed between two non-conductive or dielectriclayers 80. Channel 75 effectively serves to isolate the electricallyconductive layer 85 into two discrete sections thus forming right lead90 and left lead 95. Thus, by appropriately monitoring right lead 90 andleft lead 95 with the appropriate testing equipment, the characteristicof objects that pass through channel 75 can be determined by theireffect on these electrical characteristics. All of this assumes that asatisfactory signal to noise ratio (SNR) can be achieved for theparticular objects in question. Of course, for ease of manufacturer, theconfiguration could be reversed, that is layers of conductive materialcould sandwich the dielectric self supporting structure. Or, a singleconductive layer (split into two leads) could be formed on either sideof the self supporting dielectric layer. Such a configuration isillustrated in FIG. 4B. A silicon substrate 91 includes a partially selfsupporting silicon nitride layer 92. Two conductive layers 93, 94 aredeposited, one on either side of layer 92. This provides a simple leadstructure that allows longitudinal measurements.

[0043]FIG. 4 is a top view illustrating conductive layer 85 as it isseparated into right lead 90 and left lead 95 by channel 75. Asillustrated, right lead 90 and left lead 95 are physically separatedfrom one another by the diameter of channel 75. During the fabricationof thin film 60, this lead and channel configuration can be generated ina variety of ways. To begin with, a dielectric layer 80 is appliedthrough a sputtering or other deposition technique. Subsequently,conductive layer 85 is applied in an appropriate pattern. Such a patterncan be that of FIG. 5 or FIG. 6. Alternatively, as illustrated in FIG.4A, a single conductive layer 85 can be applied and then split into twoseparate leads 90, 95 by cutting or otherwise separating conductivelayer 85.

[0044] Referring to FIG. 5, the initial application of conductive layer85 results in a pattern that cannot be bisected merely by cuttingchannel 75 with a focused ion beam. Thus, to produce right lead 90 andleft lead 95, the area defined by FIB pattern 100 must be removed by anappropriate technique. A focused ion beam can be used to preciselyeliminate those portions of conductive layer 85 designated as removedarea 105. While this requires additional milling steps, it is not astime intensive as milling channel 75 since the thickness of theconductive layer is relatively small. Other appropriate material removaltechniques could be utilized so long as they can be defined preciselyenough to result in the electrical isolation of right lead 90 from leftlead 95 as illustrated in FIG. 4.

[0045] Once right lead 90 and left lead 95 have been so defined, asubsequent layer of dielectric material 80 may be applied completing thefabrication of thin film layer 60. The use of the various dielectriclayers 80 provides for some electrical insulation between adjacentelectrically conductive members and also serves to protect the leadsfrom physical contact or abrasion. The specific patterning orarrangement of the various dielectric layers 80 is optional so long asthe resulting thin film layer 60 includes electrically conductive leadsthat can be connected to the appropriate testing equipment and which arecapable of detecting the necessary electrical characteristics of themolecules passing through channel 75.

[0046]FIG. 6 illustrates an alternative pattern for initially formingconductive layer 85 as conductive layer 110. As illustrated, conductivelayer 110 provides for an enlarged right lead 90 and an enlarged leftlead 95 interconnected by a channel area 115. The precise dimensions ofchannel area 115 are selected so that it is effectively removed whenchannel 75 is cut therethrough by a focused ion beam, effectivelyelectrically isolating right lead 90 from left lead 95. Of course, thesame effect could be achieved by applying right lead 90 and left lead 95as separate elements with no interconnection during the depositionprocess. In either case, sufficient precision must be maintained so thatwhen channel 75 is created, right lead 90 and left lead 95 whileelectrically isolated from one another are in contact with or relativelyclose to the outer perimeter of channel 75 so as to be properly effectedby molecules passing through channel 75. It may be desirable to have theedge of the leads end prior to channel 75 so that they are not in directcontact with the fluid medium and the polymer molecules during testing.This results in a small section of dielectric material between the edgeof the leads and channel 75. Such a modification would simply requireadditional milling of the conductive layer or that an appropriateinitial pattern be applied.

[0047]FIG. 7 illustrates a quadrapole arrangement of orthogonal leadpairs 120. Orthogonal lead pairs 120 include right lead 125, left lead130, upper lead 135, and lower lead 140. All four leads are electricallyisolated from one another and abut the perimeter of channel 75. Asdescribed above, the leads can instead terminate prior to contactingchannel 75. The same techniques used for forming conductive layer 85 ofFIG. 4 are applicable to forming orthogonal lead pairs 120. The benefitof providing orthogonal lead pairs 120 is that multiple transversemeasurements can be made of the molecules passing through channel 75.Thus, measurements are not limited to a single pair of leads. Bycomparison of the output from any two lead pairs additional data can beobtained about the molecule passing therethrough.

[0048]FIG. 8 illustrates a dual conductive layer thin film 145. Asillustrated, various conductive layers 148 are disposed between variousdielectric layers 170 to form this configuration. Once again, it is theorientation of the conductive layers that is important. The particularconfiguration chosen for the dielectric layers 170 will depend largelyupon the selected deposition technique as well as the desired level ofresultant protection. In the embodiment shown in FIG. 8, a dielectriclayer 170 is disposed between the lower conductive layer and the siliconsubstrate (not shown). Additionally, another dielectric layer 170 isdisposed above the top conductive layer. Finally, a third layer ofdielectric material 170 is disposed between the two conductive layerswhich may be necessary to achieve the desired level of electricalisolation. Thus, this series of conductive layers results in a rightupper lead 150, a right lower lead 155, a left upper lead 160, and aleft lower lead 165 as viewed through a sectional view. The conductiveleads abut the outer perimeter of channel 75. Optionally, the leadscould terminate prior to contacting channel 75. Thus, as a moleculepasses therethrough, the resultant change in various electricalcharacteristics can be detected by the appropriate testing equipmentconnected to the various leads. Once again, transverse measurements canbe made (i.e., measuring across from right upper lead 150 to left upperlead 160). Additional transverse measurements can be made by measuringacross right lower lead 155 to left lower lead 165. However, the dualconductive layer thin film 145 allows for various longitudinalmeasurements to be made as well. That is, measuring across right upperlead 150 to right lower lead 155 and/or left upper lead 160 to leftlower lead 165. The introduction of longitudinal measurements allows foranother degree of measurement on the various polymer molecules passingtherethrough. Voltage and channel current can be measured in thelongitudinal direction. While two conductive layers have beenillustrated, more can be introduced as desired.

[0049]FIG. 9 illustrates quadrapole orthogonal lead pairs and a dualconductive layer thin film structure. That is, four leads are providedwhich are electrically independent from one another and abutting channel75 in a common plane. An additional four leads are provided which areelectrically isolated from one another as well as from the first fourleads. The second four leads exist in a second plane, separate andspaced apart from the first, and electrically isolated therefrom. Morespecifically, in a first plane, right upper lead 150, front upper lead185, left upper lead 160, and back upper lead 175 form a first set oforthogonal lead pairs. Disposed in a parallel plane beneath the first,right lower lead 155, front lower lead 190, left lower lead 165, andback lower lead 180 form a second set of orthogonal lead pairs. Thisconfiguration provides a large number of independent measurements thatcan be made in both the transverse and longitudinal directions. That is,any two lead pairs can be monitored and compared. In addition, multiplemeasurements can be made by comparing multiple combinations of variouslead pairs.

[0050] The previously explained embodiments are advantageous in thatthey allow for a maximum range of measurement possibilities. Onepotential drawback is the complexity of the lead patterns and the thinfilm layers. Specifically, the various leads must either be deposited ina very accurate manner, or accurate leads must be defined by a precisionmaterial removal process such as using a focused ion beam. In eitherevent, the fabrication of the thin film layer can be complex.

[0051]FIG. 10 illustrates a configuration where only longitudinalmeasurements can be made between leads existing in different,electrically isolated planes. Longitudinal measurements alone canprovide sufficient information to characterize the molecule. Asillustrated, an upper layer 205 of the electrically conductive materialis disposed above a lower layer 220 of electrically conducted material.Though not shown, upper layer 205 and lower layer 220 are separated by asufficient amount of dielectric material to assure electrical isolation.A channel 75 is cut through both upper layer 205 and lower layer 220 aswell as any existing dielectric layers. Thus, as before, passage ofpolymer molecules is allowed through channel 75. Upper layer 205includes right lead 195 and left lead 200. Likewise, lower layer 220includes front lead 210 and back lead 215. Channel 75 is cut throughthese respective layers at an area of intersection 225 where upper layer205 overlaps lower layer 220. Since only longitudinal measurements areto be made with this configuration, the precision of the previousembodiments is no longer required. Specifically, channel 75 need notelectrically isolate right lead 195 from left lead 200. Similarly,channel 75 need not electrically isolate front lead 210 from back lead215. The only measurements that can be made are in a longitudinaldirection. For example, measuring across front lead 210 to right lead195. Measurements in the transverse direction are no longer possible inthat right lead 195 is not electrically isolated from left lead 200,since a significant amount of electrically conductive material stillexists around channel 75. The same configuration occurs in lower layer220. Thus, it should become readily apparent that longitudinalmeasurements can be made between either lead of upper layer 205 toeither lead of lower layer 220. Thus, it should be further apparent thatone lead of each layer is effectively redundant and need not actually becreated. The configuration illustrated in FIG. 10 takes into accountthat it may be easier to simply apply certain patterns using thin filmdeposition techniques even though a portion of that conductive layer mayin effect be unnecessary. In any event, all that is required is that anelectrically conductive member exists in a first plane electricallyisolated from another electrically conductive member located in a secondplane. Furthermore, a channel 75 must be bored through each conductivelayer (or in close proximity thereto) and any dielectric materialexisting therebetween. Thus, the particular configuration or pattern ofthe selected leads can be selected as desired. What results is arelatively easy thin film configuration to fabricate, thus allowing fora polymer molecule characterization device to be manufactured with ahigh degree of precision on a cost effective basis.

[0052] To allow the embodiment of FIG. 10 to make transversemeasurements, upper layer 205 and lower layer 220 need only be separated(each into two leads) as indicated by the dotted lines.

[0053]FIG. 11 schematically illustrates how a completed polymercharacterization device, utilizing a dual conductive layer thin film145, would appear in a sectional view. Dual conductive layer thin film145 is attached to silicon substrate 55 having a lithography hole 65.Dual conductive layer thin film 145 essentially forms a self supportingmember in the area formed by lithography hole 65. Within the area wheredual conductive layer thin film 145 forms a self supporting member,channel 75 is bored therethrough. Thin film 145 effectively separatesupper pool 20 from lower pool 25. Using various known methods, such asapplying a voltage differential across thin film 145, polymer moleculesin one pool can be directed into the other. As they pass therethrough,they will effect the electrical characteristics of thin film 145 andthese variations will be detected by taking measurements in a transversedirection. That is, for example, from right upper lead 150 to left upperlead 160 or right lower lead 155 to left lower lead 165. Alternativelymeasurements in a longitudinal direction could be made, such as bytaking measurements across right upper lead 150 to right lower lead 155or from left upper lead 160 to left lower lead 165. Of course additionalmeasurements could be made from leads on opposite sides of channel 175which are also located in separate planes. The configuration illustratedin FIG. 11 will also be applicable to the dual layer orthogonal leadpairs illustrated in FIG. 9.

[0054]FIG. 12 illustrates the use of a simplified dual conductive thinfilm 145 which only allows for measurements in a longitudinal direction.That is FIG. 12 is illustrative of the pattern illustrated in FIG. 10 ina completed application. Measurements can be made from either right lead195 or left lead 200 to either of front lead 210 or back lead 215 (notillustrated).

[0055] Those skilled in the art will further appreciate that the presentinvention may be embodied in other specific forms without departing fromthe spirit or central attributes thereof. In that the foregoingdescription of the present invention discloses only exemplaryembodiments thereof, it is to be understood that other variations arecontemplated as being within the scope of the present invention.Accordingly, the present invention is not limited in the particularembodiments which have been described in detail therein. Rather,reference should be made to the appended claims as indicative of thescope and content of the present invention.

[0056] To obtain proper paragraph numbering after paragraph 99, useHeading 2 for the appropriate style.

What is claimed is:
 1. A device for the characterization of polymermolecules, comprising: a substrate forming a base of the device, thesubstrate including an aperture therethrough; a thin film disposed onthe substrate and extending across the aperture so that the thin film isself supporting over an area defined by the aperture; a channel throughthe thin film in the area defined by the aperture, wherein the channelis sized so as to allow passage of polymer molecules therethrough sothat as a polymer molecule passes therethrough a given monomer willcause a detectable change in the thin film wherein the detectable changewill characterize the monomer.
 2. The device of claim 1, furthercomprising a container for holding a fluid medium having a quantity ofpolymer molecules disposed therein, wherein the substrate including thethin film is disposed within the container and divides the fluid mediuminto a first pool and a second pool wherein polymer molecules aredirected from the first pool through the channel and into the secondpool by generating a voltage differential across the thin film.
 3. Thedevice of claim 1, further comprising: a first electrically conductivelayer disposed within the thin film so as to form a first set ofelectrically independent leads, wherein each lead has a first end and asecond end and the first end of each lead is proximate the channel. 4.The device of claim 3 wherein the first end of each lead of the firstset forms a portion of a perimeter of the channel.
 5. The device ofclaim 3 wherein the first set of electrically independent leadscomprises two leads positioned on opposite sides the channel.
 6. Thedevice of claim 3 wherein the first set of electrically independentleads comprises four leads positioned evenly around the channel in aquadrapole arrangement.
 7. The device of claim 3, further comprising: asecond electrically conductive layer disposed within the thin film so asto form a second set of electrically independent leads, wherein eachlead has a first end and a second end and the first end of each lead isproximate the channel.
 8. The device of claim 7 wherein the first set ofleads is separated from the second set of leads by a dielectric layer.9. The device of claim 7 wherein the first end of each lead of thesecond set forms a portion of a perimeter of the channel.
 10. The deviceof claim 7 wherein the second set of electrically independent leadscomprises two leads positioned on opposite sides the channel.
 11. Thedevice of claim 7 wherein the second set of electrically independentleads comprises four leads positioned evenly around the channel in aquadrapole arrangement.
 12. The device of claim 1, further comprising: afirst electrically conductive layer disposed within the thin film so asto form a first electrical lead; a second electrically conductive layerdisposed within the thin film so as to form a second electrical lead,wherein the second electrically conductive layer is separated from thefirst electrically conductive layer by a dielectric layer, so that thechannel is formed to pass through the first electrically conductivelayer, the dielectric layer and the second electrically conductivelayer.
 13. The device of claim 1 where the substrate is silicon.
 14. Thedevice of claim 1 wherein the aperture has micro-scale dimensions andthe channel has nano-scale dimensions.
 15. The device of claim 1 whereinthe channel has a diameter less than approximately 10 nm.
 16. A methodof forming a membrane structure for use in a device to characterizepolymer molecules, comprising: providing a support substrate of apredetermined material; depositing a thin film on the support substrate;etching a hole through the support substrate that removes all of thematerial in a predetermined area so that the thin film is selfsupporting over the predetermined area; and boring a nano-scale channelthrough a self supporting portion of the thin film.
 17. The method ofclaim 16 wherein the channel has dimensions that allow passage ofpolymer molecules therethrough so that as a polymer molecule passestherethrough a given monomer will cause a detectable change in the thinfilm wherein the detectable change will characterize the monomer. 18.The method of claim 16 wherein boring the nano-scale aperture includesusing a focused ion beam to bore the channel.
 19. The method of claim 18wherein the channel has a diameter less than approximately 10 nm. 20.The method of claim 19 wherein the thin film has a thickness of about 30nm or less.
 21. The method of claim 16 wherein the support substrate issilicon.
 22. The method of claim 16 wherein depositing the thin filmfurther includes: providing a layer of electrically conductive materialhaving a predetermined pattern such that boring the channel separatesthe layer into a plurality of independent conductive leads.
 23. Themethod of claim 22 wherein a focused ion beam is used to bore thechannel.
 24. The method of claim 22 wherein two conductive leads areformed.
 25. The method of claim 22 wherein four conductive leads areformed.
 26. The method of claim 16 wherein depositing the thin filmfurther includes: providing a layer of electrically conductive materialhaving a predetermined pattern; and removing a predetermined amount ofthe layer of electrically conductive material so that when the channelis bored, the remainder of the layer of electrically conductive materialis separated into a plurality of conductive leads.
 27. The method ofclaim 26 wherein a focused ion beam is used to remove the predeterminedamount of the electrically conductive layer.
 28. The method of claim 26wherein a focused ion beam is used to bore the channel.
 29. The methodof claim 26 wherein two conductive leads are formed.
 30. The method ofclaim 26 wherein four conductive leads are formed.
 31. The method ofclaim 16 wherein depositing the thin film further includes: providing afirst layer of electrically conductive material having a predeterminedpattern such that boring the channel separates the layer into aplurality of independent conductive leads; providing a layer of adielectric material over the first layer of electrically conductivematerial; providing a second layer of electrically conductive materialhaving a predetermined pattern such that boring the channel separatesthe layer into a plurality of independent conductive leads, wherein thesecond layer of electrically conductive material is provided such thatthe dielectric material separates the second layer of electricallyconductive material from the first layer of electrically conductivematerial.
 32. The method of claim 31 wherein a focused ion beam is usedto bore the channel.
 33. The method of claim 31 wherein two conductiveleads are formed in the first layer and two conductive leads are formedin the second layer.
 34. The method of claim 31 wherein four conductiveleads are formed in the first layer and four conductive leads are formedin the second layer.
 35. The method of claim 16 wherein depositing thethin film further includes: providing a first layer of electricallyconductive material having a predetermined pattern; removing apredetermined amount of the first layer of electrically conductivematerial so that when the channel is bored, the remainder of the firstlayer of electrically conductive material is separated into a pluralityof conductive leads; providing a layer of dielectric material; providinga second layer of electrically conductive material having apredetermined pattern, where the dielectric material separates the firstlayer of electrically conductive material from the second layer ofelectrically conductive material; and removing a predetermined amount ofthe second layer of electrically conductive material so that when thechannel is bored, the remainder of the second layer of electricallyconductive material is separated into a plurality of conductive leads.36. The method of claim 35 wherein a focused ion beam is used to removethe predetermined amount of the electrically conductive layer from thefirst layer and from the second layer.
 37. The method of claim 35wherein a focused ion beam is used to bore the channel.
 38. The methodof claim 35 wherein two conductive leads are formed in the first layerand two conductive leads are formed in the second layer.
 39. The methodof claim 35 wherein four conductive leads are formed in the first layerand four conductive leads are formed in the second layer.
 40. The methodof claim 16 wherein depositing the thin film further includes: providinga first layer of electrically conductive material; providing a layer ofdielectric material; providing a second layer of electrically conductivematerial such that the layer of dielectric material separates the firstlayer of electrically conductive material from the second layer ofelectrically conductive material and the channel passes through thefirst layer of electrically conductive material, the dielectric materialand the second layer of electrically conductive material.
 41. The methodof claim 16 wherein etching the hole includes using lithography.